The industrial use of enzymes, notably enzymes of microbial origin, has become increasingly common. Enzymes are used in numerous industries, including, for example, the starch-processing industry and the detergent industry.
It is well known that enzymes upon storage is liable to be degraded or inactivated by components (such as oxygen or bleach components) from the surrounding matrix (such as a detergent), which are capable of oxidizing or otherwise inactivating the enzyme. Further it is well known that a low formation of enzyme-containing dust of granules is desired.
Since the introduction of enzymes into the detergent industry, a lot of effort has been devoted to improving the formulation of enzyme products by applying granulation and coating of the enzyme so as to both protect the enzyme from degradation as well as control enzyme dust formation.
Many granulates are composed of a core particle upon which an enzyme containing layer is added. The core may also in itself contain enzyme. To apply the desired properties of this construction, e.g. color, dust formation, solubility rate, size, enzyme stability, physical strength etc. the core-enzyme construction is usually added additional layers of coatings providing such properties.
Some coating layers described in the art are complex multi-component compositions such as in:
WO 90/09440 which discloses an enzyme containing granulate
1) one coating (or shell) comprising a binder (e.g. kaolin), a filler (e.g. inorganic salts), granulating agents (e.g. cellulose fibers providing physical strength), and an enzyme and 2) a second dust suppressing coating (mono-, di- or triglyceride).
DE 4322229 which discloses an enzyme containing granule with a coating comprising an inorganic pigment, an alcohol, an emulsifier, a pigment dispersant and water.
JP 61162185 which discloses a process for production of an enzyme containing granule comprising coating a core with a solution containing enzyme(s), sodium sulfate and optionally binders and coating agents.
Other coating layers apply polymers or even macroscopic particles to gain improved properties of the granulate such as: WO 97/23606 which discloses an enzyme containing granule comprising an outer coating of polyvinyl pyrrolidone, PVA or PEG.
WO 96/38527 which discloses an enzyme containing granulated substance with a coating comprising water insoluble particles and a binder.
U.S. Pat. No. 5,324,649 which discloses an enzyme containing granule comprising an outer coating of polyvinyl alcohol or a copolymer.
WO 93/07263 which discloses an enzyme containing granule comprising an outer coating of vinyl (co)polymer.
WO 92/12645 which discloses an enzyme containing T-granulate coated with high melting fat or wax.
WO 89/08694 which discloses an enzyme containing granulate with a coating comprising a mono- or diglyceride of a fatty acid.
DD 263790 which discloses a protease containing granule with a coating of skim milk and/or maltodextrin.
WO 87/07292 which discloses an enzyme containing granulate with a coating containing a copolymers of acrylic acid, and/or an filler and/or a plasticiser.
EP 193829 and U.S. Pat. No. 4,689,297 which discloses a process for production of an enzyme containing particle comprising coating the particle with a macromolecular, film forming water soluble or water dispersible coating agent.
JP 58179492 which discloses an enzyme supporting particle with a coating of modified cellulose.
WO 89/08695 which discloses an enzyme containing particles with a coating containing clay.
Still other prior art disclosures apply non aqueous liquids as coatings to gain improved properties of the granulate such as:
WO 96/16151 which discloses a enzyme containing granule with a coating of a non-aqueous liquid.
Some prior art disclosures mention use of agents in a coating layers providing a special functions upon dissolution of the granulates such as:
DE 4344215 which discloses an enzyme containing granule with a coating containing an inorganic Ag-corrosion inhibitor.
EP 206417 which discloses an enzyme containing granule with a coating containing an alkaline buffer salt having a pH of 7-11. The buffer salt may constitute 50-100% of the coating.
WO 93/07263 discloses an enzyme containing granule which contains a scavenger layer, preferably ammonium sulfate.
EP-415652-A2 as well as U.S. Pat. No. 5,093,021 describes enzyme granules coated with unsoluble and highly alkaline alkali metal silicates optionally in combination with alkali metal carbonates.
Use of low molecular water soluble compounds in coatings in moderate amounts have been disclosed within the art of formulating stabile enzyme compositions usually as filler material. However, it has not been acknowledged that the amount and hygroscopicity of such compounds has essential impact on the stability of an enzyme in an enzyme granule coated with such compounds.